Recently, OLED (organic light-emitting diode) display devices have been actively developed as display devices which are thin, have high luminance and are operable at high speed. An OLED display device has a display panel which includes pixels formed of organic compound light emitting diodes. OLED display panels have a high reaction rate because no mechanical operations are performed, provide high luminance display because each of the pixels themselves emits light, and can be thin because no backlight unit is required. For these reasons, OLED display panels are favorably expected to be next generation display panels.
An organic EL light emitting layer is rapidly deteriorated when being exposed to moisture in an atmosphere, and thus needs to be sealed in against external air. Therefore, the organic EL light emitting layer has a surface covered with a transparent sealing film formed of, for example, a CVD-formed SiN film or the like, which is covered with a substrate formed of a hard transparent material such as glass or the like.
In a conventional OLED display device, a gap between the substrate and the sealing film is filled with, for example, a transparent resin (ultraviolet-curable resin, thermosetting resin, etc.) such as an epoxy resin or the like (see, for example, Patent Document 1, “Japanese Laid-Open Patent Publication No. 2010-225569”). Such a structure is provided in order to keep a certain distance between the substrate and the sealing film so that the surface of the organic EL light emitting layer and a surface of the substrate are kept parallel to each other, and also in order to prevent reflection or refraction at an interface between the substrate and the sealing film. More specifically, a resin having a relatively high pre-curing viscosity is formed in a frame shape, and a space enclosed by the resin is filled with a resin having a relatively low pre-curing viscosity. Hereinafter, in order to distinguish these resins having different functions, a resin having a relatively high pre-curing viscosity will be referred to as a “dam material”, and a resin having a relatively low pre-curing viscosity will be referred to as a “filler”.
Hereinafter, with reference to FIG. 11 through FIG. 13, a method for producing a conventional OLED display device 50 will be described. FIG. 11 shows a schematic structure of the conventional OLED display device 50. FIG. 11(a) is a planar see-through view of the OLED display device 50, and FIG. 11(b) is a cross-sectional view of the OLED display device 50 shown in FIG. 11(a). FIG. 12 is an enlarged view of part C enclosed by dashed line in FIG. 11(a). FIG. 13 shows a production step of the conventional OLED display devices 50. FIG. 13(a) is a planar see-through view showing the production step of the conventional OLED display devices 50 shown in FIG. 11(a). FIG. 13(b) is a cross-sectional view of the OLED display device 50 taken along line Z-Z′ in FIG. 13(a).
FIG. 11(a) is a planar see-through view of the OLED display device 50 showing a shape of a surface of a first substrate 51 having a dam member 53 formed thereon. The first substrate 51 is seen through a second substrate 52 and a filler 54. As shown in FIG. 11(a), the dam member 53 is formed on the first substrate 51 in a frame shape by applying a dam material thereto by use of a dispenser or the like. An area 51a of the first substrate 51 shown in FIG. 11(a) is a terminal area on which, for example, a driver for driving a TFT driving circuit layer in an organic EL light emitting layer 1 is formed. The dam member 53 is formed along an outer edge of an area of the surface of the first substrate 51 that excludes the terminal area 51a. As shown in FIG. 12, the dam member 53 is applied so as to enclose an outer edge of a display area (where effective pixels contributing to display are present) 55 which includes the organic EL light emitting layer 1 formed in the first substrate 51. The dam member 53 is provided outside with respect to the outer edge of the display area 55 in order to prevent the phenomenon that a minute refractive index difference between the dam member 53 and the filler 54 causes a refractive index distribution on the organic EL light emitting layer 1, which would distort a displayed image.
Next, a space inside with respect to the dam member 53 provided on the first substrate 51 is filled with the filler 54, and the first substrate 51 and the second substrate 52 are put together. Then, the dam member 53 and the filler 54 are cured.
In the example of FIGS. 11(a) and (b), one first substrate 51 is used to form one OLED display device. It should be noted that in an actual production method, as shown in FIG. 13(a), one first substrate 51 is used to form a plurality of OLED display devices. After the filler 54 is cured and thus the first substrate 51 and the second substrate 52 are joined together, such first substrate 51 and the second substrate 52 joined together are cut to provide individual OLED display devices 50.
In FIGS. 13(a) and (b), dashed lines A1-1 through A1-7 and A3-1 through A3-7 represent cutting lines along which the first substrate 51 and the second substrate 52 are to be cut. Dashed lines B-1 through B-5 represent cutting lines along which the second substrate 52 is to be cut. The first substrate 51 and the second substrate 52 are cut at predetermined positions along the cutting lines A1-1 through A1-6, A3-1 through A3-6, and B-1 through B-5 by use of a scribe and break technique or the like. As a result, a plurality of the OLED display devices 50 shown in FIGS. 11(a) and (b) are obtained. In FIG. 11(a), dashed line 52′ represents the position along which the second substrate 52 is located as overlapping the first substrate 51. As shown in FIG. 11(b), the second substrate 52 is not located on the terminal area 51a, and the terminal area 51a is exposed in the state of not being covered with the second substrate 52.
In the above-described conventional OLED display device 50, the dam member 53 is formed in a frame shape enclosing the display area 55. Therefore, each OLED display device 50 needs to preserve a frame-shaped area for the dam member 53 in a peripheral frame area enclosing the display area 55. This makes it difficult to decrease the size of the peripheral frame area.
In addition, in order to form a plurality of the dam members 53, the dam material needs to be applied to the first substrate 51 by use of a dispenser or the like to draw frame shapes enclosing the display areas 55 with a certain size. This step has problem of being time-consuming and also needing to be performed at high precision.
The present invention for solving these problems of the conventional structure has an object of providing a display device which can be produced by a simple method at low material cost and also has a small size of peripheral frame area, and a method for producing such a display device.